This invention relates generally to microwave circuits, and more particularly to microwave circuits for combining power from a plurality of negative resistance diode sources.
As is known in the art, a negative resistance diode, such as an IMPATT diode, is often used as an oscillator or an amplifier to convert DC power to radio frequency power. IMPATT diodes are often employed in radio frequency applications where very high output radio frequency power at very high frequencies and relatively high efficiencies is required. It is well known that the radio frequency signals provided from a plurality of IMPATT diode oscillators arranged in an appropriate manner may be combined together to provide a high power output signal, by being coupled to a common resonant cavity. As such, the IMPATT diode oscillators are positioned along the walls of the cavity to couple into the cavity equal portions of in-phase power to provide the high power output signal from the cavity. These types of resonant cavities used to combine output signals from a plurality of sources are commonly referred to as power combiners. One problem associated with use of IMPATT diodes in such power combiners to obtain such relatively high r.f. power is that when employed in such combiner circuits IMPATT diodes generally have a relatively narrow frequency bandwidth of operation. While in some applications this narrow bandwidth is tolerable and indeed sometimes desirable, in other applications a wider bandwidth for operation of the IMPATT diode is required.